Outwardly spooled multi-pole stators are known, formed by a substantially star-shaped stack of sheets featuring a plurality of poles extending from a tubular core. The stators of this type are suitable for coupling with an inner concentric armature or outer ring armature. They are common in brushless motors.
The peripheries of the poles, or pole extensions, form substantially a cylinder with a plurality of slits parallel or oblique with respect to the axis of the stator. The peripheries of the poles are connected to the core by means of pole walls that define corresponding grooves, accessible through the slits. The grooves have to be filled with insulated lead wire, by creating coils spooled about the pole walls.
At winding, where possible, the wire must pass necessarily through the slits for entering the grooves, and has to be guided to avoid collisions against the edges of the grooves. To this purpose, winding machines exist having a winding arm, or flyer, which rotates causing the wire to follow a circular trajectory and thus spooling the coil about each pole wall. The wire follows the circular trajectory while it is guided in the slits by means of special winding shrouds.
The shrouds are normally of two types, usually sufficient to wind the most common outwardly spooled multi-pole stators: a couple of lateral guiding plates, which form substantially a channel that aids the wire to enter the slits; hits are thus avoided of the wire against the edges of the poles adjacent to the pole being wound; a shroud that allows the wire to overtake the pole making substantially a double slide guide that deviates the wire from its own circular trajectory and brings it to wind about the pole wall. The shroud normally is mounted on a support shaft, that is co-axial to the flyer and is movable towards/away from the axis of the stator, for laying uniformly the wire helically about the pole wall. It can be either a whole block, or formed by two symmetrical mobile halves.
The flyer, at winding, rotates about the support shaft of the shroud in order to have its free end move in orbital position both with respect to the pole being wound and to the shroud that guides the wire in the grooves.
Every portion of wire wound about one or more poles has at least two ends. To assure the electrical contact necessary for the induction current to pass, which causes the armature to rotate and causes the motor to work, the ends have to be inserted into terminals. The terminals, in turn, when the motor is assembled, are connected to the current supply circuits for operation of the motor. The terminals are integrated in a terminal board, which is a body of plastic material that insulates axially the stack of sheets that form the ferromagnetic core of the stator.
The termination, in outwardly spooled multi-pole stators, which allow a winding by means of a flyer, is carried out in the way indicated hereinafter: before winding each pole, or plurality of in-phase poles, the flyer cooperates to put the wire ends in the terminals with a termination apparatus; at the end of winding of each pole or several poles, the outgoing wire is kept stretched by the flyer so that the termination apparatus can catch it, cooperating with the flyer for carrying out the termination, and finally cutting the wire close to the terminal, gripping the end of the wire that comes from the flyer and awaiting the start of next winding step; in the two termination steps as above described, the movement of the flyer is programmed with fractions of clockwise and/or anticlockwise rotation and with approaching motion of the stator, for cooperating with the termination apparatus and causing the wire to follow a path that approaches the terminal.
Traditionally, the termination apparatus comprises tools like lead pulls, cutters, and clamps, which move in a direction which, normally, is orthogonal to the axis of the stator. When winding stators with inner poles, by means of a reciprocating shaft with wire distribution needles, owing to the central position of the shaft, the termination apparatus can be arranged in the easiest way for catching the ends. Instead, when winding stators with external poles, with a flyer, the position of the termination tools interferes with the movement of the flyer, and they are therefore complex to arrange.
Furthermore, when the flyer moves the wire must be blocked in the terminal, to avoid that it can move away from the terminal at winding in the first coils. In fact, the movement of the flyer keeps the wire stretched while the termination is carried out. The wire can be blocked, in most of cases, at a suitable moment with a special instrument on board the machine and that engages the terminal, approaching orthogonally to the axis of the stator.
However when the terminal is located outside, on the external boundary of the stator, a tool that approaches the terminal, for blocking the wire and avoiding sliding in the terminal, would obstruct the flyer, which as said above moves in an orbital position about the pole.
On the other hand, a manoeuvre of terminating carried out without blocking the wire is risky, even with a terminal with special auto blocking shape, owing to the tension on the wire stretched by the flyer, which can cause it to disengage.
A further problem is that, when introducing an end wire in a terminal, the end protrudes of a certain amount beyond the terminal, and has to be trimmed. Thus, an off-cut wire portion would fall at the base of the machine or, where possible, in a container located underneath. This has the risk that the off-cut portion can sometimes jam into the machine or remain accidentally wound in the stator, causing in both cases a serious drawback.